Allen will start Sunday's game against the Browns and perhaps beyond that point, Nicki Jhabvala of The Athletic reports.
The Broncos are making a change at QB with Joe Flacco suffering a neck injury. A precise timetable for his recovery isn't known, but it's believed to be a multi-week issue. In Flacco's place, Allen will make his first appearance as a professional after bouncing around three organizations throughout his career.